Walker played quarterback in both college and professional football, after a brief stint in professional baseball. After high school, he was drafted by Major League Baseball's California Angels organization. He spent one year as a pitcher in the minor leagues before deciding to pursue college football. He initially attended Long Beach State but transferred when football was eliminated as a sport at the school.
He then joined the Howard University Bison, where he set single-season records for pass completions and passing yardage, as well as a single-game record for pass completions (with 38). His passing earned him the nickname "Sky Walker." He was selected to the All-MEAC (Mid-Eastern Athletic Conference) teams in both 1992 and 1993, and named Offensive Player of the Year in 1993. That season, the Bison recorded an undefeated regular season while winning the MEAC championship and a claim to the black college football national championship; the team also secured the school's first NCAA Division I-AA playoff bid and a top-ten national ranking. In 2005, Walker was voted into the Howard University Athletics Hall of Fame.
Walker pursued a professional career in the National Football League when he was selected in the 7th round of the 1994 NFL Draft by the New England Patriots. Walker spent the 1995 season in the World League of American Football with the Barcelona Dragons, where he suffered an injury during a game in which a lack of running backs required him to throw a pass on every play. Following the injury, he lost his job with New England, but he returned to the NFL with the Minnesota Vikings, where he served as a backup for two years. He attempted two career NFL passes, both for completions.